Originally posted by joensd Hi,
a good start for me was LTSpice which is freeware.
You can download it here.

You beat me to it.

I second the opinion. Free, works well, GUI obviously designed by
a programmer who understands that a program shuold be easy
to use, rather than look like a fancy Christmas tree. Besides, a lot
of people on the forum use it, so it is easy to get support here.

Can this LTspice displays the distortion curves (every order independently), or can it display the items in my first question?

LTSpice does not have quite all operations that the Spice kernel
has. However, of those things you listed, I would say you can do
everything that any other Spice implementation can do, except
noise simulation. Also LTspice lacks the built-in distorion analysis
of Spice, but I think nobody uses that anyway since it is only a
small-signal approximation AFAIK. It seems we all do distorsion
analysis by doing lenthy transient analysis and then run an FFT
on that to get a spectrum graph. Most of the things you listed
can be done in Spice, but not all of them automatically, so to speak.
DC offset is easy, you get that automatically from a DC operation
point analysis, for instance. OTOH there is no command to ask
for stability analysis. You must know how to do a correct open-
loop analysis and how to interpret it, but that is not particular
to LTSPice.

To see an example of distorsion graphs, you may have a look
for instance at the thread on "Diamond buffers w. CFP outputs"
that we started yesterday.

Just remember, a simulation is a simulation, not a real circuit.
No simulation is better than the simulator, than its models or
than the person using it.

Also some people in this forum use Circuitmaker (including me). A free student version with some limitations, most notably max 50 components in a circuit and a limited component library, can be found here: http://www.microcode.com/downloads/student.htm